mali_kbase: pm: Add adaptive power policy

Adds a new power policy 'adaptive' based off 'coarse_demand'.
The main difference is that while coarse_demand has a static
power off hysteresis (i.e. the amount of time after the GPU
goes idle that the platform idle callback is made), adaptive
scales this up and down depending on the workload.

If the GPU is frequently made active during the power off
hysteresis period, then adaptive behaves identically to
coarse_demand.

If the GPU remains idle for DEFAULT_PM_ADAPTIVE_HYSTERESIS
consecutive cycles, however, then the hysteresis period is
reduced or disabled entirely.

Bug: 183700775
Signed-off-by: Sidath Senanayake <sidaths@google.com>
Change-Id: I5619132b3e813a5b2a9420b0ff193f8aa586194a